combustion
The definition for combustion is "Act of burning." Used in a sentence: Campers must use fire with great caution to prevent combustion of the parched brush.
elusive
The definition for elusive is "Hard to grasp." Used in a sentence: The words to the song are elusive, as the singer tends to mumble.
illuminate
The definition for illuminate is "To make clear." Used in a sentence: Her excellent lecture illuminated the complicated subject of nuclear physics.
onset
The definition for onset is "Beginning." Used in a sentence: Crocuses bloom at the onset of spring, sometimes even before the snow melts.
stern
The definition for stern is "Harsh, severe." Used in a sentence: The stern principal canceled the prom after the seniors played a silly prank.